1. Stem and Root Modifications
Floral Careers Plant Propagation

2. What Exactly is a Stem?
Before we go any further in this presentation, let’s define a stem.
A stem:
is generally considered to be the central axis of the plant.
supports the leaves and flowers of a plant.
has nodes from which new shoots and sometimes new roots can arise.
is usually found above-ground, but can be modified and found below-ground as well.

3. Stem Modifications The following are stem modifications: Tubers Corms
Bulbs
Rhizomes
Stolons

4. Tubers A tuber is an underground stem that stores food.
We know a potato is a tuber because it has nodes (eyes) which produce new shoots.
A potato is a tuber

5. Corms A corm is a swollen, vertical stem with a papery covering.
Gladiolus and Crocus are examples of plants that form corms.
Crocus corms

6. Corm Growth Cycle

7. Gladiolus corms with cormels

8. Bulbs Bulbs come in 2 basic types:
Tunicate bulbs; onions and tulips are examples.
Scaly bulbs; tiger and asiatic lilies are examples.

9. Tunicate Bulbs Tunicate bulbs have:
A papery outer covering called a tunic.
A compressed, modified stem with nodes, called a basal plate.
Fleshy scales made of modified leaf tissue.
A tunicate bulb

10. Tunicate Bulbs
Fleshy Scales
Basal Plate
Onion is a tunicate bulb

11. Onion bulb shown in cross-section
Tunicate Bulbs
Tunicate bulbs form “onion rings” when cut in cross-section.
Onion bulb shown in cross-section

12. Scaly Bulbs The other type of true bulb is a scaly bulb. Scaly bulbs:
Lack a papery covering (tunic).
Have a basal plate.
Have fleshy scales made of leaf tissue.
Do not form “onion rings” when cut in cross-section.

13. Scaly Bulbs
Lilium is a scaly bulb

14. Bulb Growth Cycle

15. Rhizomes Rhizomes are: underground stems. horizontally-growing.
produce shoots and adventitious roots.
Iris rhizome

16. Rhizomes Some plants, like quack grass, produce long, thin rhizomes.

17. The pachymorph rhizome of Ginger
Rhizomes
Other plants, like ginger, produce large, thick rhizomes called pachymorphs.
The pachymorph rhizome of Ginger

18. Stolons Stolons are: Aboveground stems. Grow horizontally.
Produce shoots and adventitious roots.
Strawberry and Spider Plant are examples of plants that produce stolons.

19. Stolons
Wild Strawberry stolons

20. Root Modifications There are 2 basic types of root modifications:
Fleshy Tap Roots
Tuberous Roots

21. Fleshy Tap Roots
Carrots, beets, and radishes are examples of plants forming fleshy tap roots.
Carrots

22. Tuberous Roots Sweet potato is an example of a tuberous root.
A sweet potato is a tuberous root

23. Tuberous Roots
Dahlias are perennial bedding plants that form tuberous roots.
Dahlia

24. End